Display device including a point image

ABSTRACT

A display device of the type comprising a plurality of light sources so arranged that when various combinations of the sources are selectively energized, various luminous first symbols are produced. A luminous &#39;&#39;&#39;&#39;poing&#39;&#39;&#39;&#39; second symbol is also provided comprising a pair of intersecting filaments forming a letter X and having a size substantially smaller than the first symbols.

[56} References Cited UNITED STATES PATENTS 3,358,176 12/1967 Rosenberget al. 313/1095 3,416,020 12/1968 Carley..........................313/1095 Primary Examiner-Roy Lake Assistant ExaminerDavid OReillyAttorney-G. H. Bruestle New Providence, and Norman Lee Lindburg,Berkeley Heights, NJ.

[21] Appl. No. 820,216

Apr. 29, I969 [45] Patented Feb. 16, 1971 [731' Assignee RCA Corporationa corporation of Delaware 6 Claims, 3 Drawing Figs.

United States Patent [72] Inventors Richard Arthur Bonnette [22] Filed[54] DISPLAY DEVICE INCLUDING A POINT IMAGE ABSTRACT: A display deviceof the type comprising a plurality of light sources so arranged thatwhen various combinations of the sources are selectively energized,various luminous first symbols are produced. A luminous point secondsymbol is also provided comprising a pair of intersecting filamentsforming a letter X and having a size substantially smaller than thefirst symbols.

PATENTED FEB] a 19m mv avrans Richard A. Bonnette and Norman L. LmdburgBY 772% DISPLAY DEVICE INCLUDING A POINT IMAGE BACKGROUND OF THEINVENTION This invention relates to display devices of the typecomprising a plurality of light sources so s arranged that when variouscombinations of the sources are selectively energized, various luminoussymbols are produced.

It is desired, in certain instances, that the display devices be capableof providing a point symbol, e.g., a decimal point or period. The meansheretofore used for providing such a point symbol, e.g., a tinyincandescent bulb within the display device, are undesirably expensive.

SUMMARY OF THE INVENTION A display tube including a pair of crossedfilaments providing, when energized, a luminous image having a pointappearance when viewed at a normal viewing distance.

DESCRIPTION OFTHE DRAWING FIG. 1 is a section view of the novel displaydevice showing the light sources thereof;

FIG. 2 is a partial section of the device shown in FIG. 1; and

FIG. 3 is a section view, partly broken away, of the device showing therear connections to the light sources thereof.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION With reference tothe drawing, adisplay device is shown which comprises a transparentglass envelope 12 of a type well known in the electron tube arts. Theenvelope 12 includes a stem 14 having a plurality, e.g.,' nine, throughleads 16. Mounted on the leads within the envelope isa thin, fiatsubstrate 26 of, for example, an alumina ceramic having a dark anddullsurface to minimize light reflection.

Extending through the substrate 26, in bonded relation therewith, are aplurality of support elements or posts 28. Mounted between pairs ofposts 28 on the front" side, as viewed in FIG. 1, of the substrate 26are a plurality of elongated light sources 30.

In this embodiment, the sources 30 comprise seven filaments 33, 34, 35,36, 37, 38, and 39 ofa wire ofa refractory metal wound into coils. Theseven light sources are arranged to form adjacent rectangular arrays 42and 44' of light sources, with one of the sources 38 common to botharrays. By selectively energizing various ones of the light sources,that is, by applying a voltage between the pairs of posts 28 betweenwhich the selected sources are mounted, various luminous images orsymbols, numerals, in the instant embodiment, are obtained. For example,an image of the numeral 2 is obtained by lighting the light sources 37,35, 38, 34, and 39, each light source providing an elongated element orsegment of the composite image.

The various posts 28, as shown in FIGS. 2 and 3, are connected, on theback" side of the substrate 26, to different ones of the leads I6,whereby energizing voltages can be selectively applied to individualones of the various light sources.

To limit the number of leads 16 required for the device 10, one end ofeach of the filaments is electrically connected to a common lead 16.Likewise, to limit the number of posts 28, as well as to reduce the gapsbetween the filaments 33 and 34, and between the filaments 35 and 36, anend of each filament 33 and 34, and 35 and 36 is mounted on common posts28.

Display devices of the type to the extent so far described are generallyknown, see, for example, U.S. Pat. No. 3,416,020, issued Dec. I0, 1968,to J. A. Carley.

For the purpose of providing the display device 10 with a decimal pointimage, two filaments 52 and 54 are provided mounted between pairs ofsupport posts 56 and 58, and 60 and 62, respectively, at the bottomright of the two arrays of light sources 30. Each filament 52 and 54comprises a coil of refractory metal wire, the filaments 52 and 54 beingof substantially equal length, and the filaments 52 and 54 crossing oneanother at substantially the midpoints thereof, thus forming the letterX. Preferably, the letter X is substantially smaller in size than thecombined size of the two arrays 42 and 44 of light sources 30, and eachfilament 52 and 54 is shorter in length than any of the light sources30.

The filaments are preferably uncoated, for greater lighting efficiency,and the filaments are spaced apart in a direction normal to the face ofthe substrate 26 to prevent shorting together of the filaments.

Preferably, the two filaments 52 and 54 are electrically connected. Forexample, in the instant embodiment, the filaments are connected inseries by bending and welding together the two posts 56 and 62 on theback side of the substrate 26. The other two posts 58 and 60 areconnected to different ones of the leads 16.

Altemately, although not shown, the two filaments 52 and 54 can beconnected in series by means of a connector extending between the posts56 and 62 on either side of the substrate, the connector being aseparate strip of metal or, on the front side of the substrate, anintermediate length of a continuous coil forming the two filaments 52and 54.

When energized, the intersecting filaments 52 and 54 provide a luminousletter X. At a viewing distance, dependent upon the size of the displaydevice, the light from the branches of the X merge into a point or dotof light. The point appearance is the result of several factors, asfollows. Each post 56, 58, 60, and 62 is made of a heat conductivematerial, e.g., an alloy comprising 17 percent cobalt, 29 percentnickel, and 54 percent iron, by weight, having the trade name Kovar,"and serves as a heat sink for the filament mounted thereon. Thus, thefilaments are luminous along central portions of the lengths thereof andhave nonluminous end portions. The brightly luminous central portions ofthe filaments cross one another, thus providing a single particularlybright spot. The trailing-off of brightness of the filaments towards theposts 56, 58, 60, and 62, is at an equal rate for all four branches ofthe letter X image owing to the symmetry of the image. This contributesto the creation of acircular appearing image.

Additionally, the luminous X is substantially shorter in height than thenumerals provided by the light sources 30. In the usual operation of thedevice 10, each numeral includes at least one longitudinally extendinglight source 30 from each array 42 and 44, each numeral produced thushaving a height equal to the combined height of the arrays. In theinstant embodiment, the luminous height of the X is about one-tenth ofthe luminous height of the numerals, the luminous X having a height ofabout 60 mils, and the luminous height of the numerals being about 600mils. At a viewing distance of about 3 to 4 feet, the X appears as apoint source of light. Preferably, the height of the luminous X is lessthan one-quarter of the h one-fourth of the height of the luminousnumerals.

Preferably, the electrical impedance of each of the first light sources30 and the combined impedance of the two filaments 52 and 54 aresubstantially equal. An advantage of this is that it allows the use of asomewhat more simple and inexpensive power supply and switching circuitmeans than is possible where the impedances of the various light sourcesdiffer. In the instant embodiment, all the various filaments are formedfrom a wire of an alloy comprising 3 percent rhenium, balance tungsten,by weight, the wire having a diameter of 0.4 mil, and the wire beingwound into a coil having an outer diameter of 2.0 mils. The filaments33, 34, 35, and 36 have a length of 3 l 2 mils, the filament coilscontaining about 577 turns to the inch. The filaments 37, 38, and 39have a length of 286 mils, the filament coils containing about 630 turnsto the inch. Each filament 52 and 54 has a length of 103 mils, thefilament coils containing about 1,100 turns to the inch. The variouslight sources 30 and the decimal point image formed by the intersectingfilaments 52 and 54' are each operated at a voltage of 4.5 volts and acurrent of 25 milliamps.

A further advantage of the point" source of the instant invention isthat it utilizes rectilinear filaments which need not be bent intospecial shapes. Also, the heat sinking of the ends of the filamentsallows the use of somewhat longer filaments without increasing theluminous size of the X. The longer filaments, especially in small sizedisplay devices, are desirable as being easier to handle in the assemblyof the devices.

The point image provided by the intersecting filaments 52 and'54 is notlimited to use in display devices of the type having filamentary lightsources 30, but can be used in devices wherein the elongated lightsources comprise electroluminescent, gas discharge electrodes, or thelike. Examples of display devices in which point" light sources of thepresent invention can be used are shown, for example, in US. Pat. Nos.3,341,916, issued Sept. 19, 1967, to L. E. Greene, and 3,l60,88 l,issued Jul. 12, 1966, to S. Kuchinsky.

We claim:

1. A display device comprising:

a plurality of first light sources arranged to provide, when energized,a luminous first image; and

means for providing, when energized, a luminous point image;

said means comprising a plurality of support means and a pair offilaments, the ends of said filaments being mounte d on said supportmeans, and said filaments crossing one another intermediate the endsthereof, the luminous image produced by said filaments beingsubstantially shorter in height than said luminous first image. 2. Adisplay device as in claim l'wherein said filaments cross atsubstantially the midpoints thereof.

3. A display device as in claim 2 wherein said filaments are ofsubstantially equal length. a

4. A display device as in claim 1 wherein said filaments areelectrically connected, and the electrical impedance of each ofsaidfirst sources is substantially equal to the combined electricalimpedance of said filaments.

5. In a display device, means for producing a luminous representation ofa point comprising:

a pair of spaced apart, rectilinear electrical resistance filaments,said filaments crossing one another at substantially the midpointsthereof and being substantially of equal length;

a plurality of elements serving as combination terminal support and heatsink means for said filaments, a different one of said elements beingconnected to each of the four ends of said filaments; and

said elements being adapted to maintain end portions of said filamentsnonluminous when the central portions of said filaments are luminous.

6. In a display device as in claim 5, a plurality of elongated firstlight sources arranged to provide, when energized, a luminous firstimage and'the incandescent central portions of said filaments beingsubstantially shorter in length than said light sources.

1. A display device comprising: a plurality of first light sourcesarranged to provide, when energized, a luminous first image; and meansfor providing, when energized, a luminous point image; said meanscomprising a plurality of support means and a pair of filaments, theends of said filaments being mounted on said support means, and saidfilaments crossing one another intermediate the ends thereof, theluminous image produced by said filaments being substantially shorter inheight than said luminous first image.
 2. A display device as in claim 1wherein said filaments cross at substantially the midpoints thereof. 3.A display device as in claim 2 wherein said filaments are ofsubstantially equal length.
 4. A display device as in claim 1 whereinsaid filaments are electrically connected, and the electrical impedanceof each of said first sources is substantially equal to the combinedelectrical impedance of said filaments.
 5. In a display device, meansfor producing a luminous representation of a point comprising: a pair ofspaced apart, rectilinear electrical resistance filaments, saidfilaments crossing one another at substantially the midpoints thereofand being substantially of equal length; a plurality of elements servingas combination terminal support and heat sink means for said filaments,a different one of said elements being connected to each of the fourends of said filaments; and said elements being adapted to maintain endportions of said filaments nonluminous when the central portions of saidfilaments are luminous.
 6. In a display device as in claim 5, aplurality of elongated first light sources arranged to provide, whenenergized, a luminous first image and the incandescent central portionsof said filaments being substantially shorter in length than said lightsources.